multiplexer

Forum 2005-2010 (read only) Hardware Interfacing
#1

hi all

i imagine this is a fairly easy question; i'm not new to arduino, i just haven't done this before and i don't have the time to spend ages figuring it out... deadlines...

i have two 8-1 line multiplexers that i want to connect up to read a standard 64 grid of pressure pads.

does anyone know the code for reading this/have it handy? it must be simple, 2 'for' loops, right?

thanks

sam

#2

did you try a google search?http://www.arduino.cc/playground/Learning/4051

this is for a 4051 multiplexer, you didn't say what chips you have

#3

hi, thanks for the reply

yes, i googled; i think i understand that code, but isn't it for just one multiplexer? is the binary bit chip specific?

this:

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=4367442

is the chipset that i have...

S

#4

Yours is a digital multiplexer – the playground covers a slighlty different chip used in analog mode but the principle is similar. That playground article indicates how you can use an additional multiplexer to select from up to eight chips giving 64 inputs. It does not have the code to actually do this but there should be enough information there to work out how to do it if you can't find something closer to what you need.

Good luck

#5

i have two 8-1 line multiplexers

You can't do this with two multiplexers of the same type. One needs to be a multiplexer and the other a demultiplexer. Then it is just two 'for' loops. Look at a 74LS151 and a 74LS155 , this last chip is two 2 to 4 line demultiplexer but you can make a 1-8 demultiplexer out of it.

read a standard 64 grid of pressure pads

Remember you will also need diodes in line with each of the switch inputs if you want to remove any multi press ambiguity. You will also need to invert the output of the 74LS151 and have pull down resistors on the 74LS155.

#6